Production of gypsum wallboard



Oct. 30, 1951 l M. MPOWERS ET AL 2,573,355

PRODUCTION oF GYPSUM WALLBOARD Y Filed Feb. 18, 195o 3 sheets-sheeri MN www 5.5m: @NN WN QN\ m5, m5

YNN www Oct. 3o, 1951 M. M. POWERS ETAL 2,573,355

PRODUCTION OF GYPSUM WALLBOARD Filed Feb'. 18, 1950 3 Sheets-Sheet 2 jNVENToRs MICHAEL M.` POWERS CLARENCE ,1. LOECHL AT EY Oct. 30, 1951 M. M. POWERS .ET AL 2,573,355

PRODUCTION oF Gypsum` wALLBoARD Filed Fb. 18, 195o s sheets-shea 3 III,

565 FIG. IO

FIG.I|

40 37 Z/R 50 l l l L l l Z A INVENToRs Z/A 30 Z/R /aa 30 ZM MICHAEL M. POWERS CLARENCE LOE-CHL ATTNEY` Patented Oct. 30, 1951 OFFICE PnoDUo'rIoNgoF GYPsUM WALLBoAnn Michael M. Powers and Clarence J.'Loechl, Chicago, Ill., assignors to Certain-teed Products. Corporation, Ardmore; Pa., a corporation of Maryland Application February V1s, 195o, sei-mno. 144,952

2 Claims. l

`This invention relates to the production of gypsum wallboard. In the production of gypsum wallboard, the recognized manufacturing procedure involves depositing the wet gypsum material between two paper liners, passing these liners between rolls that determine and equalize the thickness of the board, allowing setting for gypsum of the board, cutting the continuous strip of material into predetermined lengths, and then passing these individual boards endwise through a dryingoven or kiln on single or multiple decked roller conveyors so that the heated air maybe blown across and about vboth the upper and lower faces of the board to dry the same. Y Y

Inforder to attain maximum output or production of gypsum Wallboard, such drying operation is performed at a relatively rapid rate with the temperature and humidity of the drying air such that the gypsum may be calcined by such drying air in the event that the drying operation is continued for too long a period. There is a tendency that has been long recognized in the trade for the plaster in the border areas along theedge portions of the board to be at least partially calcined in the course of the drying operation, so that in these bordering edge portions it is often found that adequate structural strength is not attained, and the soit edges are often unable to withstand handling, shipping and installation. As a result of this undesired im-v pairment in the strength and hardness of the border portions of such gypsum wallboard, it is necessary in operating a wallboard plant to constantly check the edge portions of the boards and to regulate the temperatures of the air supply so as to minimize the undesired calcination of such border portions. This problem has been recognized for many years, and efforts have been made by means of stationary sheet metal bailles within the kiln to control the flow of drying air so as to attain uniformity of drying. Theseefforts, however, have been found to be ineffective in a practical sense, and there has been no satisfactory solution heretofore which would cause the drying operation to be attained in such a way More specifically, it is an object of the present o invention to enable control of the `drying opera- Y tions to be attained in such a way that the board is' dried at substantially the same rate through- (crei-14s) out its entire width,v and a related object is enable the drying inV the edge portions of the" board to be retarded and'equalizedin respect' to the drying action in the central portions 'of the' board. yOther and related objects are to shieldv border portions ofthe board as it advances of a'simple character and which will not in` any way interfere Iwith or be broken by jamming of l the boards in the kiln. .More speciiically, it is an" object of the present invention to shield the` border portions of the: board lin a conveyor'bbiv exible means that are arranged to ride on the upper border portions ofthe board with a blaniketing eiect while being bendable in an upward direction in the event lthat a jam of boardsV in the conveyor is encountered. It is also an object` of the present invention to support such flexible'` shielding devices Within the .kiln'and in proper.`

relation to the conveyors Ain such a way-thatv these flexible shieldingelements are properly.'l

located and positioned at all times with respectA Y to the boards and are nevertheless readily remov able in the event that this is necessary.

Other and further objects of the present-in-L vention will be apparent fromy the following description and claims-and are illustrated in the accompanying drawings which, by Way of illustration, show a preferred embodiment of the' present invention and the principle thereof and what we now consider to be the best mode in which we have contempltaed applying that principle. Other embodiments of the inventionembodying the same or equivalent principle may beused and structuralr` changes may be made as desired by those'skilled in the art without departing from the present invention and the purviewA of the appended claims.

In the drawings: l

Fig. 1 is a side elevational view of a drying Fig. 4 is a fragmentary plan section taken sub-H stantially along the line 4-4 of Fig. 3;

Fig. 5 is a fragmentary vertical sectional vie'vvlv taken substantially along the line 5-5 of Fig.l3;

a lateral sense ,so that lwhentthewallboardfBv is passed through the kiln, about 3"`to '6" ofr the border portion of the board lwill be disposed beneath the blankets 30, and it will be observed that this Aaffords an additional projection `ofthe blankets B beyond the edges of the board, so

that this projecting portion of the shields 30i hangs down slightly'in an angular direction' across v,the edge of the board without actually' contacting such edge, and the remainingv por-4V tion of this projecting part of the shield is extended laterally in a subistafntially""horizontal` position and at about kthe ie'veroftho oppor faces of the rolls 2|R. This formand` locationA of the shields 30 serves as insulation for' the border portions and edges of the boards -"fr'om1 the sensible heat from the kiln structure,I and at the lsame time prevents flow of thefdrying air over and about the edges of the boards.`

Since the shields 30 are flexible in character,-

and since there may be some variationin the for each shield 30, and is attached at its lower,

end to the shield by means of a ring 31Rthat extends through the upper thickness only of the hem at the trailing edge E, this point of attachment being at what may be termed the inner edge of he shield 30 so that the ring in effect extends about the end edge of the hem. This flexible member 31 is preferably in the form of a flexible chain which will withstand the heat of the drying kilns, and the upper end of each such flexible member 31 is anchored in such a relation that the flexible member 31 of any particular shield 30 may extend upwardly past the inner side edge of the next shield 30 in the advancing direction 23. In the present instance, the anchoring means for the upper ends of the flexible members 31 is afforded by a longitudinally extending wire 40 that is mounted on the frame 35 of the conveyor, a substantial distance above the anchoring members 33, and each chain has a snap fastener 31S on its upper end which is snapped over the related wire 40.

With the shields 30 in position as above described, it will be clear that the high velocity air that moves through the kiln, and which air, of course, must finally move laterally so as to be discharged from the kiln into exhaust manifolds 24, will not move in direct contact with the upper border portions of the board that are shielded or blanketed by the shields 30, and this high velocity air is prevented by the projecting edges of the shields 30 from sweeping down across the side edges of the board Thus, the drying action is materially retarded in this border portion, and the free moisture content of the edge or border portions of the boards is maintained substantially the same as in the center portions of the board, and thus undesired calcination of these border portions of the board will be prevented even though the temperature of the drying air may be far in excess of the calcining or decomposition temperature of gypsum.

The heated drying air is dischargedr longitudinally into the kilns adjacent to the inlet ducts 24 by a plurality of longitudinally directed noz- In attaining this' result, Va down'-v 6 zles l5 that are disposed adjacent to each deck of the conveyor system, and this structure, :al-` thoughl well known inthe art, is schematically u illustrated in Fig. v2A of 'the drawings. -Since' -the drying air is discharged longitudinally of'v the kiln at a relatively high velocity from the nozzles 45, there is 'a tendency in some instances to undesirably displace the flexible blankets o1"4 shields 30, and to avoid this, a plurality of de-l ecting baffles 46 are supported as indicated in Fig. 2A soas t0 deflect the dischargeair from direct, impact on the shields 30 that are suspended adjacent to such nozzles 45. 4 f

As hereinbefore pointed out, the relative width ofl the, kiln and the conveyors 2| has a definitev bearing upon the arrangement'in whichV thev boards B are passed through the kiln,` and in many instances, vit is common practice to pass two lines of boards B longitudinally through the kiln soY that the adjacentedges B-l thereof will be relatively Aclose together as shown in Fig. l1. So long as these edges are maintained in substantial contact one with the other, the border portions of the boards adjacent to the edges B| will not be objectionably calcined in the course of the board drying operation, but in those instances where itf-is'diilicult to assure contact of the adjacent edges B-I,v the adjacentV4 border portions of the two lines of boards may be blanketed in the manner hereinbefore described in respect to the shields 30. Thus, as shown in Figs. 11, 12 and 13, a plurality of cross rods 50'are supported between locating brackets 5| that are disposed on the upper faces of the angle vmembers 2|A which support thelcon veyor rolls 2IR, and the cross bars 50 have blankets or shields |30 connected thereto, and extended downwardly therefrom, in the same manner as hereinbefore described with respect to the shields 30. The location of the shields |30 on the rods 50 is arranged so that these shields will be centered upon the theoretical location of the edges B-l of the boards. Thus, the border portions of the boards adjacent to the edges B-I will be blanketed, and the drying in these border portions will be retarded in the same manner as hereinbefore described with respect to the shields 30. In respect to the shields |30, however, the retarding action that is imposed upon the drying operation by the closeness or adjacent relationship of the two edges B|, materially reduces the need for the shields or blankets |30, and hence, in respect to these blankets |30, the number of shields |30 may be materially reduced or the spacing of the shields |30 longitudinally of the kiln may be increased substantially. Thus, it is found that where the border portions of the boards adjacent to the edges B| are maintained in substantial. contact and are blanketed or covered through, for example, onehalf of the length of the kiln, the resulting drying operation will attain substantial uniformity in all of the portions or areas of the boards B.

From the foregoing description, it will be apparent that the present invention materially simplifies the drying of gypsum wallboard and the like, and assures that uniformity of product will be attained. It will also be evident that by reason of such uniformity of drying, the structural strength in such boards will be uniform. Under and in accordance with the present invention, this uniformity of drying is attained by means which will not of themselves tend to create jams of boards within the kiln, and yet if such jams occur, the blanketing or shielding 1r means may be readilyandeasly removed so as: to ifaeilitatezremovalyof' thefdamaged boards:y

Thus, whilefwe have-illustrated and;descr-ibed the;preferredyembodiment of our invention', .itf-r isltobe;understood thatvthisis oapableof vara,- tiorr. andmodificationi and*I We` l-i'fhereiore do not- Wsh=tobe limitedto .the-precise details set orth, but desirevto avail ourselvessofsuch changesiand alterations-as fall within theplwview.,of.A tl'leffol;` lowing; claims. L

1.In: a drying apparatus for vrallboar-,d` an-A elongated drying kilm a; conveyor mounted inA saidI kilnand along; which?.Wallboard;..1Tiay.V be

.10 pend said@ Inemlziersr; within said kiln aiulfover:

Ysaid conveyor iii-.position to extend downwardly; onto .,and, alongV the upper bordering surfaces`J off suchf wallboa'rd asi; they? Wallboard is advancedthrougli said kiln byf said; conveyor so asi-toy moved in; a horizontalcpositionl; langitudinal,of4 15; blahketisuhrbrdeing surfaces and thereby re:-

said kiln, af plnrality'ofindividual heatresistant, iiexible blanket members.: each. having ani an:v chorineendland-a trailing end, anel'ls'ringineansM.v at: spaced; interi/als? along saidL conveyor`` and tard.dryingI ontheborder portions of the .vvlallfe board, L and .fiexiblaguid elements l'connected to? theQ trailing-:ends of, said blanket memberst andf extended upwardly.v past adjacent side .edg e5.o f, -A

spaced;upwardlyv therefromi means seeuring theyzg adiacenti/blanketmembers t0 guide and nsllje anchoring ends of saidblanket ,membelsg to said., anchoring-means :to suspend saidfmembers Wtbim said' kiln` andover said; conveyor-2impositionto ride along the upperrborderingsurfaces ofsuch- Wallboard as the Wallboard isradvaneed t-ln'ouglfi; said kiln by-said conveyor soasftofthereby..-- re` tard` dryingon therborderf portions; offtherfwalll boa-id; and r iiexible guide elements connected; to l tlief trailingv ends:` ofsaidi blanketl members, and extended upwardlyr past: adjacent: side edges ofiv adjacentblanket` members to gnideand insuret proper tracking-of said blanket members:

2a Iny a; drying` apparatus for Wallboand, an elongated drying; kiln;A a, conveyor` including ai.

propentrackingofisa'id blanket members.A

lxgLCHAEL .M. POWERS,

CLARENCE J. LOECHL.

,REEERENCES CITED UNITED 1 STATES VJPA-'I'ENTS- 30.: Number Namel Datei.

" 1,2063594 Rim Nov.- 28,-.1916VT 1,214,234 v Skinner i Jan. 3o, 1917` 1,730,529. Ruler Oene, 1,929'r 1,975,687. Grabiii w .k oet. 2, 192341; 

1. IN A DRYING APPARATUS FOR WALLBOARD, AN ELONGATED DRYING KILN, A CONVEYOR MOUNTED IN SAID KILN AND ALONG WHICH WALLBOARD MAY BE MOVED IN A HORIZONTAL POSITION LONGITUDINAL OF SAID KLIN, A PLURALITY OF INDIVIDUAL HEAT RESISTANT FLEXIBLE BLANKET MEMBERS EACH HAVING AN ANCHORING END AND A TRAILING END, ANCHORING MEANS AT SPACED INTERVALS ALONG SAID CONVEYOR AND SPACED UPWARDLY THEREFRON, MEANS SECURING THE ANCHORING ENDS OF SAID BLANKET MEMBERS TO SAID ANCHORING MEANS TO SUSPEND SAID MEMBERS WITHIN SAID KILN AND OVER SAID CONVEYOR IN POSITION TO RIDE ALONG THE UPPER BORDERING SURFACES OF SUCH WALLBOARD AS THE WALLBOARD IS ADVANCED THROUGH SAID KILN BY SAID CONVEYOR SO AS TO THEREBY RETARD DRYING ON THE BORDER PORTIONS OF THE WALLBOARD, AND FLEXIBLE GUIDE ELEMENTS CONNECTED TO THE TRAILING ENDS OF SAID BLANKET MEMBERS AND EXTENDED UPWARDLY PAST ADJACENT SIDE EDGES OF ADJACENT BLANKET MEMBERS TO GUIDE AND INSURE PROPER TRACKING OF SAID BLANKET MEMBERS. 